Over the years, numerous methods have been proposed for improving the delivery of biologically active agents, particularly small molecule drugs. Challenges associated with the formulation and delivery of pharmaceutical agents can include poor aqueous solubility of the pharmaceutical agent, toxicity, low bioavailability, instability, and rapid in-vivo degradation. Although many approaches have been devised for improving the delivery of pharmaceutical agents, no single approach is without its drawbacks. For instance, commonly employed drug delivery approaches aimed at solving or at least ameliorating one or more of these challenges include drug encapsulation (such as in a liposome, polymer matrix, or unimolecular micelle), covalent attachment to a water-soluble polymer (i.e., conjugation) such as polyethylene glycol (i.e., PEG or PEGylation), use of gene targeting agents, and the like.
PEGylation has been employed to improve the bioavailability and ease of formulation of small molecule therapeutics having poor aqueous solubilities. For instance, water-soluble polymers such as PEG have been covalently attached to artilinic acid to improve its aqueous solubility. See U.S. Pat. No. 6,461,603. Similarly, PEG has been covalently attached to triazine-based compounds such as trimelamol to improve their solubility in water and enhance their chemical stability. See International Patent Application Publication No. WO 02/043772. Covalent attachment of PEG to bisindolyl maleimides has been employed to improve poor bioavailability of such compounds due to low aqueous solubility. See International Patent Application Publication No. WO 03/037384. Polymer conjugates of non-steroidal anti-inflammatory drugs (NSAIDs) and of opioid antagonists have also been prepared. See U.S. Patent Application Publication Nos. 2007/0025956 and 2006/0105046, respectively. Prodrugs of camptothecin having one or two molecules of camptothecin covalently attached to a linear polyethylene glycol have also been prepared. See U.S. Pat. No. 5,880,131. Prodrugs of irinotecan and docetaxel having (among other things) four molecules of drug covalently attached to a multi-arm polymer have been described in U.S. Pat. No. 7,744,861 and International Patent Application Publication No. WO 10/019233, respectively.
Certain drugs, such as the alkaloids, are notoriously difficult to solubilize. Such alkaloids include the taxanes. Cabazitaxel is a drug within the taxane class of anti-cancer agents that is approved in combination with prednisone for the treatment of individuals suffering from hormone-refractory metastatic prostate cancer who are were previously treated with a docetaxel-containing treatment regimen.
The chemical name of cabazitaxel is (2α,5β,7β,10β,13α)-4-acetoxy-13-({(2R,3S)-3-[(tertbutoxycarbonyl)amino]-2-hydroxy-3-phenylpropanoyl}oxy)-1-hydroxy-7,10-dimethoxy-9-oxo-5,20-epoxytax-11-en-2-yl benzoate, which has the following chemical structure:
Commercially, cabazitaxel is available as the acetone solvate under the JEVTANA® brand from Sanofi-aventis (Bridgewater, N.J.). This commercially available form also includes Polysorbate 80 as a solubilizing agent for the drug.
Although shown to provide several advantages over other taxanes (such as docetaxel) for certain indications, cabazitaxel is also associated with drawbacks as well. For example, cabazitaxel has a toxicity profile that is similar to docetaxel and is believed to be dependent on both the rate of drug clearance from the body as well as the patient's cytochrome CYP3A4 metabolic activity. In this regard, patients given a standard dose of cabazitaxel exhibit a wide interpatient variation in clearance and toxic effects, thereby supporting the concept that interpatient differences in metabolic activity accounts for at least some of this variance.
In addition, administration of cabazitaxel and other conventional taxane-based therapeutics may not distribute to the desired areas in vivo. In this regard, these conventional molecules may distribute relatively evenly throughout a patient's body, thereby exerting their effects on both normal and cancerous tissues. It would be desirous, however, if cabazitaxel and other conventional taxane-based could be modified in such a way so as to accumulate in tumor tissues while still retaining their potent anti-cancer effects.
The present invention seeks to address these and/or other needs.